Precast and prestressed concrete structural sections can be formed by pouring concrete into a form which will mold the concrete into the desired shape. A common application of this technology is in the formation of floor and roof sections for car parking garages and other buildings which include a horizontal deck portion with downwardly extending leg or stem sections to add strength to the molded concrete. A common form used for molding the concrete into this shape is a double leg form which is normally constructed of steel.
The conventional double leg form has a horizontal surface for forming the top of the section of the molded concrete, commonly called the deck, and downwardly and inwardly sloped surfaces for forming the leg sections of the molded concrete. The leg section of the double leg form must generally slope downwardly and inwardly to permit ready release of the molded concrete upon hardening. A common slope for the leg section of the double leg form is one in twenty-two. However, many other slopes are used.
In repeated molding using any concrete form, the ability to clean the form after use to prepare it for the next mold is highly critical. After the molded concrete is removed from the form, particulate matter, such as concrete particles and dust, and chemicals such as release agents, remain on the form surface and must be removed before concrete is again poured into the mold. Generally, the horizontal surfaces of the form can be readily cleaned, including the portion forming the deck section of the molded concrete and the bottom of the leg sections of the form. However, the sloped sides of the leg section of the form are quite difficult to clean.
The industry has attempted to develop apparatus for cleaning the sloped sides of a leg section form. U.S. Pat. No. 3,562,832, issued to Rickard on Feb. 16, 1971, illustrates one example of such an attempt. This patent discloses the use of horizontal brushes for cleaning the horizontal surfaces of a leg form and conical leg brushes which attempt to clean the sloping sides of the leg sections of the form. It can be readily understood that as the conical leg brushes wear, their cleaning action against the sloped sides of the leg section of the form becomes less effective. The Rickard patent discloses the use of adjustable height wheels on the machine driving the brushes which function to actually lower the apparatus and brushes to compensate for wear of the brush elements. However, wear on the leg brushes and horizontal brushes will not be equal. Therefore, adjustment of the wheels to move the entire apparatus downward will not adjust out the differential wear. Because the drive shafts of the Rickard device (both the horizontal brush drive shafts and leg brush drive shafts) are mechanically connected, it would be impractical to adjust the brushes independently. In addition, only limited movement of the machine is permitted and the entire brush must be disposed of once the limit of movement of the adjustable wheels is used up.
Several other shortcomings are present in the Rickard device. The mechanical linkage between the horizontal and leg brush drive shafts makes it difficult to change brush size and brush shape to clean other form shapes with different slopes, widths and depths in the leg section. Also, with its multiple brushes and complex linkage, the Rickard device is relatively large, heavy and expensive. It would probably require a crane to pick it up for movement to another form. The Rickard device also devotes too much attention and resources to cleaning the deck, when the most difficult parts to clean are the tee sections. Finally, longer forms, commonly called "long line" forms, are generally not perfectly straight. The leg surfaces and top outside edge rails may well be nonparallel. The Rickard device does not appear to have any ability to adjust the spacing of the leg brushes relative to the horizontal brushes. Therefore, as the device travels along the form, the pressure exerted on the leg surfaces by the leg brushes may vary and the leg brushes may even lose contact with a surface on the leg, resulting in poor and nonuniform cleaning.
A need therefore exists for an apparatus for effectively cleaning the sloped sides of a leg section of a form which overcomes the disadvantages of the prior device disclosed in U.S. Pat. No. 3,562,832. The apparatus should be able to follow the leg surfaces while maintaining equal cleaning pressure against the surfaces. The improved device should provide economical cleaning with a minimum of maintenance, service and adjustment by the operator.